What term describes the proportion by which the capacitance increases when an insulator is placed between the plates of a capacitor?

The term that describes the proportion by which the capacitance increases when an insulator is placed between the plates of a capacitor is the dielectric constant. The dielectric constant is a dimensionless number that reflects how much a material can increase the capacitance of a capacitor compared to a vacuum. When an insulator, or dielectric material, is inserted between the plates of a capacitor, it reduces the electric field within the capacitor and allows more charge to be stored, which in turn increases the capacitance.

In practical terms, the dielectric constant indicates how effective a particular material is as an insulator and its ability to allow electric fields to penetrate through it. Materials with higher dielectric constants allow for greater increases in capacitance when used in capacitors, thus enhancing their storage capability.

This definition and context underscore the critical role of the dielectric constant in capacitor design and performance in electrical engineering.